Despite a decreased muscle mass and strength, UCP1-tg mice display a healthy metabolic phenotype characterized by increased energy expenditure, delayed diet-induced obesity development, reduced hepatic steatosis, browning of white adipose tissue, and improved glucose homeostasis, leading to an increased lifespan on obesogenic diets, and increased overall longevity [16, 17, 117, 118]. This evidence concerns the gene UCP1 and obesity due to melanocortin 4 receptor deficiency.